Device for vehicle lighting

ABSTRACT

Poor visibility at night is a stressful and dangerous situation, dreaded by many drivers. The frequency of accidents is decidedly higher at night as a result of poor visibility, compared with driving during the day and with good visibility. An improvement of visibility at night is achieved by using systems which, in addition to the normal headlights, have two “laser headlights” which use laser diodes emitting in the near infrared range as a light source. In order to minimize the space requirement for the laser headlights in addition to the normal headlights, a device is described in which, in an inventive way, the light beam used for lighting is deflected by a deviating prism and a reflector. It is conceivable to design the device such that the reflector emits the light beam in a direction which is rotated by approximately 90 degrees with respect to the direction of incidence of the light beam into the deviating prism. It is possible in this way to place the light source or the light beam supply directly behind the reflector, thereby creating a flat, space-saving structure in the lighting device by using a bent beam path.  
     However, the device is also suitable for stationary applications, in particular in or on buildings.

DESCRIPTION

[0001] Poor visibility at night is a stressful and dangerous situation, dreaded by many drivers. The frequency of accidents is decidedly higher at night as a result of poor visibility, compared with driving during the day and with good visibility. The use of the low beam, because of oncoming traffic, results in low visibility which is misjudged by many drivers. This results in late recognition of unlighted obstacles, pedestrians, bicyclists without light, and animals, thus resulting in accidents. In addition, the lights of oncoming vehicles and their reflection glare the driver, in particular when the road is wet; i.e., the driver briefly drives into a black hole. Particularly at risk here are night-blind drivers and older drivers because of their reduced sight. Rain, fog, and snowfall make the visibility conditions even worse.

[0002] An improvement of visibility at night is achieved by using an optoelectronic system as described in German Offenlegungschrift 40 07 646.6.

[0003] The system records a video image of a scene and displays it to the driver in a suitable form. The displayed image shows substantially more than the driver may see directly through the windshield with his eyes. In addition to the normal headlights, the system has two “laser headlights” which use laser diodes, emitting in the near infrared range, as a light source. Since infrared light is almost invisible to the human eye, such lighting may be used “in the permanently turned-on position.” However, the necessary extra space for the laser headlights in addition to the normal headlights is a disadvantage.

[0004] The object of the present invention is to provide a device for vehicle lighting requiring little space.

[0005] The object is achieved by using a device for vehicle lighting in which the light beam emitted, used for lighting, is deflected by a deviating prism and a reflector.

[0006] It is conceivable according to the present invention to design the device such that the reflector emits the light beam in a direction which is rotated approximately 90 degrees with respect to the direction of incidence of the light beam into the deviating prism. It is possible in this way to place the light source, i.e., the light beam supply, directly behind the reflector, thereby creating a flat, space-saving structure in the lighting device by using a bent beam path. The light beam may advantageously be supplied to the device via a light guide, but it is also conceivable to generate the light beam by using a laser light source which is contained in the device itself. The use of a laser as a light source has the advantage of a narrow-band illumination, making it possible to dimension the optical elements, contained in the lighting device according to the present invention, in a particularly accurate manner and adapted to the desired beam path.

[0007] The present invention is explained in greater detail in the following based upon FIGS. 1 through 5 and an exemplary embodiment in which a laser is used as a laser source.

[0008]FIG. 1 shows the top view of a laser headlight according to the present invention (section through plane E-F of FIG. 2).

[0009]FIG. 2 shows the top view of a laser headlight according to the present invention, alternatively to the one in FIG. 1 (section through plane E-F of FIG. 2).

[0010]FIG. 3 shows the rear view of a laser headlight according to FIGS. 1 or 2 (section through plane A-B of FIG. 1).

[0011]FIG. 4 shows an exemplary front view of a laser headlight according to FIGS. 1 or 2 (section through plane A-B of FIG. 1).

[0012]FIG. 5 shows an enlarged drawing of an advantageous reflector face of component 3 (reflector/diffuser)

[0013]FIG. 6 shows an enlarged drawing of an advantageous reflector face of component 3, as an alternative to the one in FIG. 5 (reflector/diffuser)

[0014] It is apparent in FIG. 1 and FIG. 2 that the headlight according to the present invention may have an extremely flat design.

[0015] In FIG. 1, reflector/diffuser 3 and deviating prism 2 are each designed as a separate component. Laser diode 1 is located on a heat sink on the rear side of the headlight and sends the light in the direction of lens 4. Through this lens 4, the light subsequently hits a deviating prism 2. From there the light arrives in reflector/diffuser 3, via which it is beamed out.

[0016] The embodiment of the device according to the present invention illustrated in FIG. 2 is essentially equivalent to the device illustrated in FIG. 1; however, diffuser 3 and deviating prism 2 are manufactured here as a one-piece component 5.

[0017] After emission, the light of laser diode 1 widens through diffraction. For the sake of clarity, the light beams emitted by the laser diode are depicted with dashed lines in FIGS. 1 and 2. It is conceivable here that by using a laser diode in the form of a Fabry-Perot diode, the light beams widen in one direction only by a small angle of +5° (FIG. 1), while they widen in the other direction by an angle of +20° (FIG. 2). Laser 1, used as a light source, is to be advantageously dimensioned such that the emitted light beam is widened on its way to lens 4 in such a way that the surface of lens 4 is optimally lighted. Surface-emitting laser diodes may be used here in an advantageous manner as light sources. Since these laser diodes have a symmetrical light emission, the dimensions of the headlight are to be advantageously adapted to the diode face; however, it is also conceivable to operate several laser diodes next to one another, in order to enlarge the light emission area.

[0018] Laser diodes emit the light out of a very small area of 1 μm to 200 μm ; the light spot may thus be considered to be punctiform. The laser diode is situated in the focal point of a planar-convex lens 4 which collimates the diverging light beam. The lens may be a simple lens, a Fresnel lens, or an achromatic lens, for example.

[0019] A deviating prism 2 deflects the light beam by approximately 180° and feeds it into a plate 4 whose inside is designed as a reflector and whose outside is designed as a diffuser.

[0020] A possible embodiment of the reflector is outlined in FIG. 5. In this drawing, after reflection, the light strikes the surface of the diffuser which is situated above the undulated, saw-tooth-like structure of the reflector perpendicularly. This is not necessary, since the light may also incide at a different angle when an appropriate shape of reflector is used. A preferred direction is parallel to the axis of the vehicle, but for better lighting of curves, other directions are also reasonable. The light, coming from the left out of deviating prism 2, is reflected on a saw-tooth-like microstructure of reflector 3. This results in a maximization of the lighted surface of the structure. The lighting of the surface of the structure is outlined in FIG. 5. The microstructure may be manufactured by molding. By using laser diodes as a light source, coherence in time and space is so minor that no undesirable interference effects occur.

[0021] The diffuser may be designed as a holographic diffuser, but it is also conceivable in an advantageous manner to integrate the diffuser into the structure of the reflector, whereby, as is apparent in FIG. 6, the undulated, saw-tooth-like structure is used with micro lenses or micro wedges. The diffuser forms the desired headlight distribution from the incoming collimated light beam. It is conceivable in a particularly inventive way to design the reflector, i.e., the diffuser, such that it has several zones of different reflectivity and diffusion properties. It is advantageous if the device is designed such that the light beam may be guided in a way that only certain zones of lens 4 and thus only certain zones of reflector 3 are lighted.

[0022] The device for vehicle lighting according to the present invention is of course not limited to mobile use in vehicles, but it may also be advantageously used in stationary applications, in particular in or on buildings. The device may therefore serve, for example, as a particularly flat back lighting for advertising signs and other graphic displays. It is also conceivable to use the device according to the present invention in an advantageous manner as a flat, integratable illumination for relatively thin media (e.g., walls in houses), or as a lighting wall or illumination of closet interiors or refrigerators. 

What is claimed is:
 1. A device for vehicle lighting, wherein the light beam, used for lighting, is divertedly emitted using a deviating prism and a reflector.
 2. The device as recited in claim 1, wherein the reflector emits the light beam in a direction which is rotated by approximately 90 degrees with respect to the direction of incidence of the light beam into the deviating prism.
 3. The device as recited in one of claims 1 or 2, wherein the light beam is generated by a laser light source which is contained in the device itself.
 4. The device as recited in claim 3, wherein the laser light source is designed as a Fabry-Perot diode.
 5. The device as recited in claim 3, wherein the laser light source is designed as a surface-emitting laser diode.
 6. The device as recited in claim 5, wherein several surface-emitting laser diodes are operated in parallel for enlargement of the light emission area.
 7. The device as recited in one of claims 1 or 2, wherein the light beam is supplied to the device via a light guide.
 8. The device as recited in one of claims 1 through 7, wherein the light beam is supplied to the deviating prism via a lens.
 9. The device as recited in claim 9 [sic; 8], wherein the lens and the deviating prism are manufactured in one piece.
 10. The device as recited in one of claims 1 through 9, wherein the light beam may be guided so that only certain zones of the lens, and thus only certain zones of the reflector, are lighted.
 11. The device as recited in one of claims 1 through 10, wherein the reflector, for targeted guiding of the light beam, has an undulated, saw-tooth-like microstructure.
 12. The device as recited in claim 11, wherein the surface of the reflector is designed such that it simultaneously acts as a diffuser, the individual sections of the undulated, saw-tooth-like microstructure of the reflector lighted by the light beam being designed as micro lenses or micro wedges.
 13. The device as recited in one of claims 11 or 12, wherein the reflector has several zones with different reflectivity properties.
 14. Use of a device as recited in one of claims 1 through 13, for stationary applications, in particular in or on buildings. 